The invention relates to an oil pump assembly for a vehicle lubrication system comprising a pumping device and a relief valve arranged to communicate with a pump outlet and with a relief deposit location. The invention also relates to an internal combustion engine system comprising an internal combustion engine and an oil pump assembly, a method of controlling an oil pump assembly, a computer program, a computer readable medium, and a controller.
Traditional vehicle oil pumps may be driven via a belt or a gear assembly by the crankshaft of the vehicle internal combustion engine. Such oil pumps might in some operational situations deliver more pressure than is required by the devices served by the pump. For example, at cold starts a primary object of an engine lubrication system could be for the oil to increase its temperature, and hence its efficiency as quickly as possible. Therefore, at cold starts it might be desirable for oil to reside longer than usual at the lubricated devices, such as engine bearings, and to not be replaced at a relatively high rate by cold oil from the pump. Delivering more pressure than is required by the lubricated devices, e.g. at certain engine speeds and loads, also entails excessive energy consumption by the oil pump.
Systems have been developed to vary the pressure of the oil provided to the lubricated devices of the engine. For example, U.S. Pat. No. 5,339,776 discloses an oil pump which draws oil from an oil sump, and a valve which can divert oil supplied by the oil pump back into the oil sump without routing the oil to the lubricated devices.
U.S. Pat. No. 6,488,479 suggests that where high pressure oil is dumped back into the sump, aeration of the oil may occur, and the oil dumped back to the sump might experience significant heat loss. Said U.S. Pat. No. 6,488,479 discloses a pressure release valve which has a spring loaded plunger, and can redirect a portion of the flow that exits an outlet port of an oil pump back to an inlet port of the pump. A plunger adjustment mechanism is provided in the form of a solenoid subassembly that includes a housing and a solenoid winding. When the solenoid winding is energized, the plunger moves so as to provide communication between the outlet and inlet ports. Such a solenoid winding needs to work against the spring force, and introduces an undesired increase of complexity of the oil pump. Said U.S. Pat. No. 6,488,479 alternatively suggests, with reference to FIG. 4, providing the plunger adjustment mechanism similar to a hydraulic actuator, with a “head” serving as an actuation piston, which is provided in a housing, forming a seal with the piston. On opposite sides of the piston the housing is provided with apertures for fluid communication for the piston actuation. Also in this alternative the plunger adjustment mechanism needs to work against the spring force, and therefore needs to be sized therefore. Further, the hydraulic actuation needs an arrangement which is relatively complex and sensitive to wear, e.g. due to the seal between the piston and the housing.
It is desirable to provide an energy efficient, yet simple and reliable manner of varying the pressure of oil provided to the lubricated devices of a vehicle engine.
According to an aspect of the invention, an oil pump assembly is provided for a vehicle lubrication system comprising a pumping device, the oil pump assembly presenting an outlet leading from the pumping device, and an inlet leading to the pumping device, the oil pump assembly further comprising a relief valve presenting a valve chamber arranged to communicate via an outlet relief passage with the outlet, and to communicate via a relief deposit passage with a relief deposit location, the relief valve further comprising a plunger located in the valve chamber, the plunger being movable between a closed position, in which communication between the outlet relief passage and the relief deposit passage is prevented, and an open position, in which communication between the outlet relief passage and the relief deposit passage is provided, the oil pump assembly further comprising a control valve for controlling the relief valve, characterised in that it comprises a control passage adapted to provide a communication between the outlet and the control valve via the valve chamber.
The pumping device can be provided in any suitable form, for example as a gear pump, a gerotor pump or a rotary vane pump. As understood, the oil pump assembly outlet allows oil pumped by the pumping device out of the oil pump assembly, e.g. to an oil filter before proceeding to lubricated engine devices and an oil sump. As also understood, the inlet of the oil pump assembly can allow oil to the pumping device, e.g. from the oil sump. It should be noted that in the closed position, the plunger might block the outlet relief passage and/or the relief deposit passage. Also, in the open position, the outlet relief passage and the relief deposit passage may be exposed to the valve chamber.
Thus, the invention provides for a control passage providing a communication between the outlet and the control valve via the valve chamber. The control passage extending via the valve chamber of the relief valve provides in a simple manner the possibility of using the pressure in the pump outlet to adjust the actuation of the plunger and thereby control the relief valve. Compared to known art this provides a simplified and more durable relief valve control arrangement with fewer parts. Thus an effective oil pump output pressure control is provided with only a small increase of the complexity of the lubrication system. Further the invention can be implemented on a traditional oil pump of any sort, so that a simple and durable pump can be used.
The oil pump assembly may comprise a pump body housing the pumping device, the pump body presenting the outlet leading from the pumping device, and the inlet leading to the pumping device.
Preferably, the control valve is configured to communicate, e.g. via a control pressure deposit passage, with a control pressure deposit location, whereby the control valve is arranged to control a communication between the outlet and the control pressure deposit location via the valve chamber. Preferably, the control pressure deposit location is provided in the inlet. Thereby, oil used for control of the relief valve will be transported back to the inlet of the oil pump, which reduces the energy consumed by the pump. Alternatively, the control pressure deposit location can be provided in an oil sump of the lubrication system.
In some embodiments, the outlet relief passage and the control passage are configured to communicate with the valve chamber on opposite sides of the plunger. Opposite sides of the plunger preferably means opposite sides of the plunger in the direction of movement of the plunger in the valve chamber. This means that a pressure in the outlet can be, when the control valve prevents communication between the valve chamber and the control pressure deposit location, distributed to one side of the plunger via the outlet relief passage and to the opposite side of the plunger via the control passage. The interface between the valve chamber and the relief deposit passage can be provided laterally to the direction of movement of the plunger. For example, where the valve chamber is cylindrical, the interface between the valve chamber and the relief deposit passage can be provided in the cylindrical surface of the valve chamber. Thereby, in the closed position the plunger can block the relief deposit passage. Further, the interface between the valve chamber and the outlet relief passage can be provided in an end portion of the valve chamber. Thereby, the relief valve is arranged so that a pressure via the outlet relief passage can exert an opening force on the plunger towards the open position thereof. In the open position the relief deposit passage can be exposed to the valve chamber.
In some embodiments, the relief valve is configured so that the plunger can be urged from the closed position to the open position by pressure in the control passage. Thereby, the control passage can present an outlet control passage portion connecting the outlet with the valve chamber. The interface between the valve chamber and the outlet control passage portion can be provided in an end portion of the valve chamber. Thereby, the plunger is configured to be urged from the closed position to the open position by pressure in the outlet control passage portion.
The control passage can be configured to communicate with the valve chamber on opposite sides of the plunger. Thereby, when the control valve prevents communication between the outlet and the control pressure deposit location, the outlet pressure will be provided on both sides of the plunger by the control passage, when the plunger is in the closed position. On the other hand, when the control valve allows communication between the outlet and the control pressure deposit location, and the pressure in the control pressure deposit location is lower than in the outlet, the pressure will fall at a side of the plunger which is then in communication with the control pressure deposit location. Thereby a pressure difference will occur across the plunger so that it is moved towards the open position.
In some embodiments, the relief valve is arranged so that a communication is provided in the valve chamber between opposite sides of the plunger. Thereby, a portion of the control passage can be provided in the valve chamber and provide a communication between opposite sides of the plunger. This provides for other portions of the control passage to communicate with the valve chamber on opposite sides of the plunger, as suggested above. Thus, in such embodiments, at least a part of the communication provided by the control passage between the outlet and the control valve, is provided in the valve chamber between opposite sides of the plunger.
The communication in the valve chamber between opposite sides of the plunger can be provided by a bore in the plunger. For example, where the plunger has a cylindrical external surface, the bore could be centrally located in the plunger and straight in the direction of movement of the plunger between the closed and open positions. Alternative arrangements are possible for providing the communication in the valve chamber between opposite sides of the plunger. For example, a groove could be provided in the external surface of the plunger or in the surface of the valve cavity.
In some embodiments, the outlet relief passage is provided by the control passage. Thereby, the outlet relief passage and the control passage can be provided together in a joint conduit, which simplifies the design of the oil pump assembly. The interface between the valve chamber and the combined outlet relief passage and control passage is advantageously provided in an end portion of the valve chamber.
In some embodiments, the plunger presents a recessed portion between two end portions of the plunger, so as to provide with the valve chamber an intermediate space between the end portions. The two end portions is preferably aligned in the direction of movement between the open and closed positions. Where the relief valve is configured so that the plunger can be urged from the closed position to the open position by pressure in the control passage, the interface between the valve chamber and the outlet relief passage can, similarly to the interface between the valve chamber and the relief deposit passage, be provided laterally to the direction of movement of the plunger. For example, where the valve chamber is cylindrical, the interface between the valve chamber and the outlet relief passage, as well as the interface between the valve chamber and the relief deposit passage, can be provided in the cylindrical surface of the valve chamber. Thereby, the relief valve may be configured so that in the closed position, the plunger blocks, with one or both of the end portions, the outlet relief passage and/or the relief deposit passage, and in the open position, the outlet relief passage and the relief deposit passage may be exposed to the intermediate space.
Preferably, the relief valve comprises an elastic element, which may be provided as a spring. The elastic element can be configured to exert a closing force on the plunger towards the closed position. Thereby, the plunger is biased by the elastic element towards the closed position. The relief valve can be arranged so that a pressure via the outlet relief passage and/or the outlet control passage portion can exert an opening force against the closing force of the elastic element, (the outlet control passage portion being a part of the control passage connecting the outlet with the valve chamber). Thereby, said pressure can tend to move the plunger towards the open position. For example, the elastic element and an interface between the valve chamber and the outlet control passage portion and/or the outlet relief passage can be located on opposite sides of the plunger.
Preferably, the plunger is configured to delimit a subspace of the valve chamber, in which subspace the elastic element is located. It is understood that the size of the subspace varies due to plunger movement. Preferably, where the control valve is configured to communicate with a control pressure deposit location, the control valve is arranged to control a communication between the outlet and the control pressure deposit location via the subspace. The control passage extending via the relief valve subspace, which is delimited by the plunger, and in which the elastic element is located, provides an effective and simple manner of using the pressure difference between the pump outlet and the control pressure deposit location to adjust the actuation of the plunger and thereby control the relief valve. As stated, the control pressure deposit location is advantageously provided in the pump inlet.
When the control valve is controlled so as to isolate the control pressure deposit location from the subspace, the pressure in the subspace will be that of the outlet. As a result, the pressure on both sides of the plunger will be equal, and when there is an over-pressure in the outlet, this will assist the elastic element in urging the plunger to the closed position. By selective control by the control valve, the control passage can provide the communication between the outlet and the control pressure deposit location via the subspace. This will decrease the pressure in the subspace, and as a result, the opening force from the outlet pressure can move the plunger against the closing force of the spring towards the open position.
Where the elastic element is provided in the form of a spring, with a given spring strength, it is possible to regulate the relief valve with a higher pressure than in said FIG. 4 solution in U.S. Pat. No. 6,488,479. This is because the pump outlet pressure acts on the spring side of the relief valve plunger when the control valve is closed. To accomplish this in said solution in U.S. Pat. No. 6,488,479, the spring has to be increased, which will require that the energy needed to regulate a reduction of the pressure of the pump outlet needs to be increased.
Preferably, the control valve is not arranged to isolate the outlet from the valve chamber. Thus, where the control passage presents an outlet control passage portion connecting the outlet with the valve chamber, preferably the control valve is not located along the outlet control passage portion.
Preferably, the plunger presents a recessed portion between two end portions of the plunger so as to provide the valve chamber with an intermediate space between the end portions,
wherein the plunger is configured to delimit, on one side of the plunger, a subspace in the valve chamber, and, opposite to the subspace, a pressure space in the valve chamber, and wherein the control valve is arranged to communicate with the subspace, and the relief valve is arranged so that a communication is provided in the valve chamber between the intermediate space and the pressure space
Thereby, the outlet relief passage may be arranged to communicate with the intermediate space in the valve chamber. This is advantageous since it allows the outlet relief passage to extend from the valve chamber perpendicularly from the latter. This in turn allows the outlet relief passage to be provided as a straight conduit, which simplifies manufacturing of the oil pump assembly. The reason is that the conduit can be provided without angles which may complicate machining of a work piece from which a body housing the relief valve is manufactured.
Preferably, the communication between the intermediate space and the pressure space is provided by at least one cavity in the plunger. The cavity is preferably elongated. The cavity may be provided as a bore in the plunger and/or as an elongated recess on the plunger surface forming a conduit with the surface of the valve chamber.
Preferably, the at least one cavity providing the communication between the intermediate space and the pressure space extends in parallel with a direction of movement of the plunger in the valve chamber. This is advantageous since it allows for a plurality of such cavities, provided, e.g. as bores and/or elongated recesses, in one of the end portions of the plunger and radially outside of the intermediate portion, to be parallel. This, in turn, facilitates manufacturing of the plunger, since the latter can be kept in the same orientation during machining of said cavities.
Preferably, at least one of the at least one cavity providing the communication between the intermediate space and the pressure space extends perpendicularly to a direction of movement of the plunger in the valve chamber. Preferably said cavity extending perpendicularly to a direction of movement of the plunger in the valve chamber, extends through the intermediate section of the plunger.
The communication provided in the valve chamber between the intermediate space and the pressure space is particularly advantageous where the outlet relief passage is provided by the control passage. More specifically, the relief valve may be arranged so that a communication is provided in the valve chamber between opposite sides of the plunger, and the outlet relief passage may be provided by the control passage.
Thus, the outlet relief passage and an outlet control passage portion may be combined into a single conduit between the pump outlet and the relief valve. Also, the outlet relief passage may communicate with the valve chamber at a location between ends of the cylinder presented by the valve chamber. It is understood that the communication in the valve chamber between opposite sides of the plunger is a communication between the pressure space and the subspace. This communication can be direct, or indirect, e.g. via the intermediate space. It is also understood that the outlet relief passage communicates with the intermediate space in the closed position of the plunger.
Combining the outlet relief passage and the control passage into a single conduit between the pump outlet and the relief valve simplifies manufacturing of the oil pump assembly, since machining steps for providing a conduit can be omitted. In addition, since the combined outlet relief passage and control passage may communicate with the valve chamber at a location between side ends of the cylinder presented by the valve chamber, the combined outlet relief passage and control passage may be manufactured as a straight conduit, preferably extending perpendicularly to the valve chamber main extension. This further simplified manufacturing, since no angle need to be provided in the combined outlet relief passage and control passage.
It is understood that the valve chamber may present an elongated, preferably cylindrical, shape, and the plunger may be adapted to move in the longitudinal direction of the valve chamber.
The communication in the valve chamber between opposite sides of the plunger may be provided by one or more cavities in the plunger. For example, the communication between the intermediate space and the pressure space, and the communication between opposite sides of the plunger are provided by at least one cavity, preferably at least two cavities, e.g. bores or recesses, in the plunger.
Said cavities may be provided in the end portions of the plunger, radially outside the recessed portion of the plunger. Thereby the communication in the valve chamber between opposite sides of the plunger is provided by combination of the communication between the intermediate space and the pressure space and a communication between the intermediate space and the subspace. Said cavities are preferably elongated and parallel, mutually as well as with the valve chamber.
In some embodiments, said cavities include at least one cavity extending in a longitudinal direction of the valve chamber, from the pressure space to the subspace, and at least one cavity extending through the recessed portion of the plunger, transversely to and intersecting said at least one cavity extending in the longitudinal direction of the valve chamber.
Preferably, at least one of the at least one cavity providing the communication between intermediate space and the subspace is a bore with a diameter of 0.5-5.0 mm, preferably 2.0-3.0 mm. Thereby, the bore(s) is/are large enough to prevent congestion of debris, but small enough to keep the flow through them relatively small.
Preferably, the relief deposit location is provided in the inlet. Thereby, the recirculated oil will be transported back to the inlet of the oil pump, which substantially reduces the energy consumed by the pump. It should be noted however that the invention is applicable to lubrication systems where the relief deposit location is provided elsewhere, for example in the oil sump.
Preferably, the control valve is a proportional valve. This further simplifies and increases the reliability of the solution for controlling the relief valve.
Preferably, the assembly according comprises a pump body housing the pumping device, the pump body presenting the outlet leading from the pumping device, and the inlet leading to the pumping device, wherein the control valve is spatially located externally of the pump body the control valve. In many lubrication systems the oil pump is located in or at the oil sump, which can provide a harsh environment with high temperatures, oil mist, etc. When locating the control valve externally of the pump body, or even remotely from the pump body, the pump body can be located in or at the oil sump, and the control valve can be located externally of the oil sump. This makes it possible to provide a location for the control valve at which it is not subjected to the environment of the oil sump. In turn, this makes it possible to use a valve without consideration for it having to withstand said environment, which simplifies and reduces the cost for the assembly.
It should be noted that the relief valve is preferably located in the pump body. However, alternatively, the relief valve can be located externally of the pump body.
According to another aspect of the invention, an internal combustion engine system is provided comprising an internal combustion engine and an oil pump assembly according to any embodiment of the invention, wherein the control valve is mounted externally on a vehicle engine comprising lubricated devices served by the oil pump assembly. This makes it possible to provide the control valve at a location in which it is easy to access, for example for service or replacement.
According to another aspect of the invention, a method is provided of controlling an oil pump assembly according to any embodiment of the invention, comprising determining a value of a lubrication parameter indicative of the operation of the vehicle lubrication system, and controlling, at least partly based on the determined lubrication parameter value, the control valve so as to control the communication between the outlet and the control pressure deposit location via the subspace.
According to another aspect of the invention, a computer program is provided comprising program code means for performing the steps of said method of controlling an oil pump assembly when said program is run on a computer. According to another aspect of the invention, a computer readable medium carrying is provided a computer program comprising program code means for performing the steps of said method of controlling an oil pump assembly when said program product is run on a computer. In addition, according to another aspect of the invention, a controller is provided being configured to perform the steps of said method of controlling an oil pump assembly.